Abstract
Basal monocots exhibit considerable variation in inflorescence and floral structure. In some cases,
such as Triglochin maritima, it is not clear whether the lateral and terminal structures of the inflorescence
are flowers or pseudanthia, or where the limits between flowers and inflorescence lie. To address
these questions, morphological studies were carried out, and the results show that in T. maritima both
terminal and lateral structures are flowers, not pseudanthia. The terminal flower of T. maritima develops
from the apical inflorescence meristem, suggesting that the apical meristem identity changes
from ‘‘inflorescence'' to ‘‘flower'' during inflorescence development. In addition, distal flowers of T.maritima are reduced, and there is no distinct flower-subtending bract; instead, the perianth develops
are reduced, and there is no distinct flower-subtending bract; instead, the perianth developsunidirectionally, resulting in an abaxial-median bract-like tepal and bilaterally symmetrical flowers,
similar to those of other basal monocots, such as Aponogeton and Acorus. It is possible that the leaf
primordium changes its positional homology from ‘‘flower-subtending bract'' to ‘‘tepal.'' Therefore,
in some basal angiosperms with abbreviated development of lateral flowers the demarcation of the
flower vs. the inflorescence is ontogenetically ambiguous. In situ hybridization experiments show that
a putative ortholog of the B-class gene APETALA3/DEFICIENS is expressed in developing stamens
and carpels, and may also be expressed in the shoot axis of the very young inflorescence. This
expression pattern seems to be consistent with the gradual transition between inflorescence and flower
that was observed morphologically.
Originalsprog | Engelsk |
---|---|
Tidsskrift | Aliso |
Udgave nummer | 22 |
Sider (fra-til) | 107-125 |
ISSN | 0065-6275 |
Status | Udgivet - 2006 |
Bibliografisk note
Key words: APETALA3, basal angiosperms, fading borders, gene expression pattern, Juncaginaceae,MADS-box gene, monocots, organ identity, Triglochin.